1. Field of the Invention
The invention relates to a semiconductor device and somewhat more particularly to a semiconductor device which includes raised solderable contacts and a protective passivation layer along with a method of producing such a semiconductor device.
2. Prior Art
U.S. Pat. No. 3,761,309 (which corresponds to German DOS 2,032,872 and is assigned to the assignee of the present invention) discloses a method of producing a semiconductor body whereby metal contacts are provided on the body and the free body surface areas and the metal contacts are coated with an insulating layer which is then removed from the metal contacts. Thereafter, at least two different metal layers are applied onto the contacts, with the outer metal layer being composed of a soft-solderable metal and being of a thickness substantially greater than that of the underlying metal layer. The excess metal remaining on the surface of the insulating layer is removed via a photo-lacquer etching process. With this prior art method, a semiconductor element or body is provided in a generally known manner with a conductor path structure composed of, for example, Al and the entire surface of the resultant structure is coated with a SiO.sub.2 layer. Thereafter, at least a portion of the Al contact structure is uncovered via conventional photo-etching techniques. Then, a relatively thin layer of, for example, Ti is applied over the entire surface of the resultant structure and then a layer of Au is deposited onto the Ti layer. The Au layer is galvanically reinforced or thickened after a photo-lacquer mask is applied, exposed and developed to protect the surface of the resultant structure at all areas except where the soft-solderable metal contacts are desired. Next, the protective photo-lacquer mask is removed and the metal layers above only the SiO.sub.2 layer are etched away so that a raised solderable contact is provided. This prior art patent also discloses that the gold surface can be protected from solder by chemically precipitating Ni and/or Sn onto the gold surface.
Commonly assigned U.S. Ser. No. 540,458, filed Jan. 13, 1975, discloses a semiconductor device having a protective layer consisting of a heat-stabilized photo-lacquer material. In accordance with those teachings, a photo-lacquer is applied as a protective layer and is first heat-tempered at a temperature in the range of about 100.degree. to 210.degree. C. and preferably at 190.degree. C. and then heat-tempered at a temperature in the range of 190.degree. to 300.degree. C. and preferably at 250.degree. C.